TUESDAY, April, 15, 2014 (HealthDay News) -- Just in time for summer swimming and boating season comes a grim government report: Drowning deaths are still a problem in the United States, even though overall deaths from drowning are down.

"Death rates overall have declined 9 percent, but for those aged 45 to 84, it increased 9.7 percent," said report author Dr. Jiaquan Xu, an epidemiologist at the U.S. National Center for Health Statistics (NCHS) at the U.S. Centers for Disease Control and Prevention.

At highest risk for drowning are still children under age 5 and adults aged 85 and older, Xu said.

In the study, the researchers looked at the years 1999 through 2010. In all, more than 46,000 people died from unintentional drowning during that time, including boating accidents.

Xu also computed drowning death rates for every 100,000 people by age brackets for the 12-year period, finding the biggest increase in rates among those aged 45 to 84. Those aged 5 to 19 were least likely to drown, Xu suspects, because they probably already learned how to swim.

Xu said the high risk among those aged 4 and younger is probably due to lack of swimming ability or a lack of supervision by babysitters and parents.

The investigators found some surprises when they looked at how drowning risk varies by the day of the week. They suspected weekends would be a higher risk than weekdays, partly due to kids being out of school with more free time, but the level of increased risk was not expected. "It was a surprise to me that it was 48 percent higher on the weekend," Xu said.

Locations of drowning differed by gender, Xu's team also found. The location for girls' and women's drownings were about equally divided among the bath tub, swimming pool, natural water and unspecified locations.

Boys and men were most likely to drown in a natural water setting, with more than half the fatalities occurring there, the report found. Next most likely were unspecified locations, then swimming pools and, lastly, bath tubs.

Locations of the drowning also varied by age, the findings showed. Drowning happened most often in a bath tub for those under age 1 and age 85 and above. The swimming pool was the most likely place of death for children aged 1 to 4. Those aged 5 to 84 were most likely to drown in natural water settings.

The report was published in the CDC's April edition of the NCHS Data Brief.

"The CDC report highlights the need for qualified supervision in all aquatic settings, especially natural water," said Tom Gill, a spokesperson for the U.S. Lifesaving Association. The report reminds folks to seek out water areas guarded by certified lifeguards, he said.

Swimming near a lifeguard reduces the risk of drowning, said B. Chris Brewster, president of the U.S. Lifesaving Association (USLA). "USLA statistics consistently indicated that the chance of drowning death at a beach protected by lifeguards is one in 18 million beach visits," he said.

Xu added that parents and caregivers should "keep an eye on the kids," whether indoors or outdoors and near bodies of water.

Gill agreed. "Parents must maintain constant supervision over children in aquatic settings," he said. Parents who aren't qualified to protect their children or themselves should be sure to swim only when qualified lifeguards are present, Gill added.

The American Red Cross has additional tips for safe swimming:

Wear a U.S. Coast Guard-approved life jacket if you are inexperienced as a swimmer, but don't rely on the jackets alone.

Enroll in learn-to-swim courses.

Secure a home pool with appropriate barriers.

If a child turns up missing, check water sources first, since seconds count.